This invention relates to an electromagnetic operating system for operating the processing of objects, including an operating member responding with a delay having a duration to which a tolerance applies. The invention further relates to a method for electromagnetically controlling an operating member responding with a delay having a duration to which a tolerance applies.
Such an electromagnetic operating system and such a method for operating the processing of objects are known from practice, for instance in the form of an operating system with an electromagnetically operated wrap spring clutch, and in the form of operating an operating member using such a clutch, respectively.
An example of an electromagnetic wrap spring clutch is a clutch of the type EC20 which is commercialized by Reell Precision Manufacturing Corporation, St. Paul, Minn., U.S. In the use of such clutches, the accurate control of the moment at which the clutch in effect engages is of great importance in various applications, for instance because this determines when a transport roller for transporting sheets of paper is set in motion, thereby determining, for instance, in what relative position with respect to another object an object is added to a transport along a path.
In many other applications an accurate control of the time at which an operating member is set in motion is of great importance as well, such as operation of a nip in which an envelope is retained or transported back to cause it to buckle (see, for instance U.S. Pat. No. 5,899,050) and operations of folding knives with which one or more sheets can be urged into the nip between a pair of folding rollers (see, for instance, U.S. Pat. No. 4,985,013).
A problem of such electromagnetic operating systems is that the delay with which the operating member responds to the alteration of the electric voltage condition the coil is in, varies from one specimen to another, which does not enable sufficiently accurate control of when the operating member is moved. This plays a role in particular when the response of the operating member in turn comprises a further action, such as operating, engaging or carrying along a further part.
It is known to limit the spread of response times of an electromagnetically controlled or driven operating member by limiting manufacturing tolerances, but this generally entails a substantial increase in cost and contributes little to counteracting the drift of the response time as a result of alterations in operating conditions and as a result of running in and wear.
It is an object of the invention to provide a low cost solution which enables a more accurate determination of the moment at which an operating member is moved or stopped and by which drift of the response time as a result of altered conditions or running in or wear can be limited in a simple manner.
This object is achieved according to the present invention by providing an electromagnetic operating system for operating the processing of objects, including: at least one coil for converting an electric current into a movement; an operating member movable in response to an alteration larger than a minimum voltage change of an electrical voltage condition across the coil, for operating the processing of objects, the operating member operatively responding to the alteration with a delay having a duration to which a tolerance applies; and a control system for effecting alterations of the electrical voltage condition across the coil; wherein the control system is arranged for generating different test command pulses having dimensions including a duration and a voltage, the test command pulses each comprising effecting an alteration of the voltage condition larger than the minimum voltage change, which test command pulses are of mutually different magnitude as regards at least one of the dimensions thereof and at least one of the test command pulses having a duration shorter than the delay; for registering a command code in accordance with a smallest magnitude test command pulse having caused the operating member to move; and for subsequently applying corrections in accordance with the registered command code to the alterations in the voltage condition for operating the operating member when in operation.
This object can further be achieved according to the present invention by providing a method for electromagnetically controlling an operating member for operating the processing of objects, including making an alteration larger than a minimum voltage change to an electrical voltage condition across a coil, such that the operating member for operating the processing of objects is moved, the operating member operatively responding to the alteration of the voltage condition with a delay having a duration to which a tolerance applies; further including the steps of:
generating different test command pulses having dimensions including a voltage and a duration, the test command pulses each including effecting an alteration of the voltage condition larger than the minimum voltage change, which test command pulses are of mutually different magnitude as regards at least one of the dimensions and at least one of the test command pulses having a duration shorter than the delay;
registering a command code in accordance with a smallest magnitude test command pulse which has caused the operating member to move; and
subsequently applying corrections in accordance with the registered command code to the alterations in the voltage condition for operating the operating member when in operation.
By making use of test command pulses of which the magnitude is varied so as to determine the minimum magnitude test command pulse causing the operating member to respond, in a simple manner an indication is obtained of the delay of the operation of the operating member or regarding the manner in which the command is to be carried out to achieve a predetermined delay. It is, for instance, not necessary to measure the delay, and whether the operating member moves or not can be established with simple sensors, or can be simply established by service personnel through the senses or with very simple equipment.
Particular exemplary embodiments of the invention are set forth in the dependent claims.
Hereinafter, further objects, embodiments, advantages and details of the invention are described on the basis of a few exemplary embodiments, referring to the drawings.